This invention relates to purification of ketones.
Acetone is produced in a number of ways most of which result in an acetone having undesirable by-products. While the instant invention is applicable to purification of any crude acetone such as produced by fermentation of isopropanol. Crude acetone compositions produced in decomposition of cumene hydroperoxide to produce phenol is of particular interest.
Crude acetone generally contains aldehydic substances such as formaldehyde, propionaldehyde and acetaldehyde. When such substances are present, the acetone fails commonly used tests for purity such as the National Formulary (NF) acetone test using potassium permanganate.
A number of methods of purification of acetone are reported. For instance, Joris in U.S. Pat. No. 2,624,699 reports heating crude acetone with activated carbon, graphite, diatomaceous earth, asbestos, pumice, coke, magnesia and sulfonated phenol-formaldehyde anion exchange resins impregnated with an alkali metal hydroxide and separating the so-treated acetone from its impurities. In U.S. Pat. No. 2,597,497 Joris reports a combination of distillation and extraction. Brundege in U.S. Pat. No. 3,668,256 reports continuously distilling crude acetone in a single, multiple-plate distillation tower in which a dilute alkaline solution mixes with the down flowing liquid so that said liquid remains rich in acetone and no other liquid phase is formed. In that process crude acetone is fed into a column through a feed inlet located in the lower section of the column above the stream source and below the alkali feed inlet. The alkali mixes with the downflowing liquid in the column forming a single, acetone-rich liquid phase which contacts the upflowing vapors of acetone and aldehydes, converting the aldehydes to nonvolatile polymers which tend to settle in the bottom of the column with water and the spent alkali. These polymers, however, are an undesirable by-product. In addition, the alkali results in increased conversion of acetone to diacetone alcohol and mesityl oxide.
It would be desirable to purify acetone such that formation of diacetone alcohol and/or mesityl oxide is substantially reduced or avoided. Diacetone alcohol is observed to convert to mesityl oxide such that a concentration of diacetone alcohol in acetone plateaus and the remainder converts to mesityl alcohol.